Remember you have 2 kinds of blocks: even or odd. In this case you are matching Even and Odd numbers for this block

300 Avondale AVE ZIP Code Plus 4

The U.S. Postal Service introduced an expanded Monterey Park ZIP code system that it called ZIP+4, often called "plus-four codes", "add-on codes", ZIP Plus 4 Monterey Park - CA, or "add ons". A ZIP Plus Four Code (ZIP+4) uses the basic Zip code plus four additional digits related to Avondale AVE to identify a geographic segment within the five-digit delivery area, such as a the 300 to 398 Avondale AVE street block, a group of apartments, an individual high-volume receiver of mail or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery in California.

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The postal code from addresses 300 to 398, applies to residential houses, business, buildings, and every property with Even and Odd numeration in this range.